38 Questions
What is the result when fertilization does not occur?
The egg degenerates, and menstruation occurs
Where does the process of fertilization occur?
In the ampullary region of the uterine tube
What is the purpose of capacitation?
To condition the sperm to penetrate the corona cells
What triggers the acrosome reaction?
Binding to the zona pellucida
What is the function of the acrosome reaction?
To facilitate the penetration of the zona pellucida
What is the purpose of Phase I of fertilization?
To penetrate the corona radiata
What is the function of the zona pellucida?
To facilitate and maintain sperm binding
What happens to the permeability of the zona pellucida during fertilization?
It changes when the head of the sperm comes in contact with the oocyte surface
What is the purpose of the acrosome reaction?
To expose the posterior region of the sperm head
What is the result of the fusion of the sperm and oocyte membranes?
Restoration of the diploid number of chromosomes
What happens to the cells during cleavage?
They decrease in size with each division
What is the name of the cluster of cells that forms after four initial cell divisions?
Morula
What is the term for the process of rapid cell divisions after fertilization?
Cleavage
What is the term for the cells that derive from cleavage up to the blastula stage?
Blastomeres
What is the term for all structures that develop from the zygote, both embryonic and extraembryonic?
Conceptus
What is the branch of biology that studies the development of gametes, fertilization, and development of embryos and fetuses?
Embryology
What is the result of the zona reaction?
Alteration of the properties of the zona pellucida
At what stage of development is the embryo termed a fetus?
Beginning of the ninth week
What is the duration of the normal period of gestation?
38 weeks
What is the term for the study of congenital disorders that occur before birth?
Teratology
During which week of development does the concept shift from a single-celled zygote into a multi-leveled, multi-dimensional fetal body plan?
Eighth week
What is the term for the process by which the fertilized egg develops into an embryo?
Human Embryogenesis
What is the process that occurs after fertilization, resulting in the formation of a multicellular embryo?
Mitotic cleavage
What is the term for the stage of development during which the embryo has more recognizable external features and a more complete set of developing organs?
Fetus
What is the term used to describe the solid sphere of cells within the zona pellucida?
Morula
What is the primary function of the trophoblast layer?
To surround the inner cell mass and blastocoel
What is the term used to describe the process of the blastocyst burrowing into the endometrium?
Invasion
What is the first cavity formed during embryonic development?
Blastocoel
When does implantation typically occur?
During the first and second week of gestation
What is the term used to describe the stage of embryonic development where fluids penetrate the zona pellucida?
Blastulation
What is the primary function of the corpus luteum after ovulation?
To release female sex hormones, including progesterone and estrogen
What is the term for the cluster of cells that surround the oocyte in the ovarian follicle and after ovulation?
Cumulus oophorus
What is the result of the LH surge in the ovulation process?
The release of the oocyte from the follicle
What is the purpose of the fimbriae of the uterine tube?
To transport the ovum to the uterus
What happens to the endometrium if fertilization does not occur?
It degenerates
What is the term for the structure that forms from the ruptured follicle after ovulation?
Corpus luteum
What is the result of the failure of the blastocyst to implant within the endometrium?
The degeneration of the endometrium
What is the term for the layer of cells that surrounds the oocyte after ovulation?
Corona radiata
Study Notes
Embryology
- Human embryogenesis is the process by which a fertilized egg develops into an embryo, studying the development of gametes, fertilization, and development of embryos and fetuses.
- Human embryology specifically studies development during the first eight weeks after fertilization.
Gamete Approximation and Fertilization
- Ovulation is the process by which a mature egg is released from the ovary, triggered by a surge of luteinizing hormone (LH).
- The released egg is covered by the zona pellucida and one or more layers of follicular cells.
- Fertilization occurs in the ampullary region of the uterine tube, involving capacitation, the acrosome reaction, and penetration of the corona radiata and zona pellucida.
Capacitation and Acrosome Reaction
- Capacitation is a period of conditioning in the female reproductive tract, allowing sperm to pass through corona cells and undergo the acrosome reaction.
- The acrosome reaction, induced by zona proteins, releases enzymes needed to penetrate the zona pellucida.
Phases of Fertilization
- Phase I: Capacitated sperm pass through the corona radiata.
- Phase II: Sperm penetrate the zona pellucida, releasing acrosomal enzymes.
- Phase III: Fusion of oocyte and sperm cell membranes occurs.
Results of Fertilization
- Restoration of the diploid number of chromosomes occurs, with half from the father and half from the mother.
- The sex of the new individual is determined, with an X-carrying sperm producing a female embryo and a Y-carrying sperm producing a male embryo.
- Initiation of cleavage occurs, resulting in rapid cell divisions with no significant growth.
Cleavage and Morula Formation
- Cleavage results in a cluster of cells called the morula, with at least four initial cell divisions producing a dense ball of at least sixteen cells.
- The morula forms within four days as it travels to the uterine cavity.
Blastulation (Blastocyst Formation)
- The morula develops into a blastocyst, consisting of an inner cell mass (ICM) and an outer layer of cells called the trophoblast.
- The blastocoel is a fluid-filled cavity formed within the blastocyst.
Implantation
- Implantation is a complex biochemical and mechanical process that begins in the first week of gestation and extends into the second week.
- The process involves apposition, attachment, and invasion of the blastocyst into the uterine wall.
This quiz covers the basics of human embryology, including embryogenesis, fertilization, and development of embryos and fetuses. It also touches on congenital disorders that occur before birth.
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